linux/arch/x86/mm/pageattr_64.c

/*
 * Copyright 2002 Andi Kleen, SuSE Labs.
 * Thanks to Ben LaHaise for precious feedback.
 */

#include <linux/highmem.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/mm.h>

#include <asm/processor.h>
#include <asm/tlbflush.h>
#include <asm/uaccess.h>
#include <asm/io.h>

pte_t *lookup_address(unsigned long address, int *level)
{
	pgd_t *pgd = pgd_offset_k(address);
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

	if (pgd_none(*pgd))
		return NULL;
	pud = pud_offset(pgd, address);
	if (!pud_present(*pud))
		return NULL;
	pmd = pmd_offset(pud, address);
	if (!pmd_present(*pmd))
		return NULL;
	*level = 3;
	if (pmd_large(*pmd))
		return (pte_t *)pmd;
	*level = 4;

	pte = pte_offset_kernel(pmd, address);
	if (pte && !pte_present(*pte))
		pte = NULL;

	return pte;
}

static struct page *
split_large_page(unsigned long address, pgprot_t prot, pgprot_t ref_prot)
{
	unsigned long addr;
	struct page *base;
	pte_t *pbase;
	int i;

	base = alloc_pages(GFP_KERNEL, 0);
	if (!base)
		return NULL;
	/*
	 * page_private is used to track the number of entries in
	 * the page table page have non standard attributes.
	 */
	SetPagePrivate(base);
	page_private(base) = 0;

	address = __pa(address);
	addr = address & LARGE_PAGE_MASK;
	pbase = (pte_t *)page_address(base);
	for (i = 0; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE) {
		pbase[i] = pfn_pte(addr >> PAGE_SHIFT,
				   addr == address ? prot : ref_prot);
	}
	return base;
}

void clflush_cache_range(void *addr, int size)
{
	int i;

	for (i = 0; i < size; i += boot_cpu_data.x86_clflush_size)
		clflush(addr+i);
}

static void flush_kernel_map(void *arg)
{
	struct list_head *l = (struct list_head *)arg;
	struct page *pg;

	__flush_tlb_all();

	/* When clflush is available always use it because it is
	   much cheaper than WBINVD. */
	/* clflush is still broken. Disable for now. */
	if (1 || !cpu_has_clflush) {
		wbinvd();
	} else {
		list_for_each_entry(pg, l, lru) {
			void *addr = page_address(pg);

			clflush_cache_range(addr, PAGE_SIZE);
		}
	}
}

static inline void flush_map(struct list_head *l)
{
	on_each_cpu(flush_kernel_map, l, 1, 1);
}

static LIST_HEAD(deferred_pages); /* protected by init_mm.mmap_sem */

static inline void save_page(struct page *fpage)
{
	if (!test_and_set_bit(PG_arch_1, &fpage->flags))
		list_add(&fpage->lru, &deferred_pages);
}

/*
 * No more special protections in this 2/4MB area - revert to a
 * large page again.
 */
static void revert_page(unsigned long address, pgprot_t ref_prot)
{
	unsigned long pfn;
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t large_pte;

	pgd = pgd_offset_k(address);
	BUG_ON(pgd_none(*pgd));
	pud = pud_offset(pgd, address);
	BUG_ON(pud_none(*pud));
	pmd = pmd_offset(pud, address);
	BUG_ON(pmd_val(*pmd) & _PAGE_PSE);
	pfn = (__pa(address) & LARGE_PAGE_MASK) >> PAGE_SHIFT;
	large_pte = pfn_pte(pfn, ref_prot);
	large_pte = pte_mkhuge(large_pte);

	set_pte((pte_t *)pmd, large_pte);
}

static int
__change_page_attr(unsigned long address, unsigned long pfn, pgprot_t prot,
		   pgprot_t ref_prot)
{
	struct page *kpte_page;
	pgprot_t ref_prot2;
	pte_t *kpte;
	int level;

	kpte = lookup_address(address, &level);
	if (!kpte)
		return 0;

	kpte_page = virt_to_page(kpte);
	BUG_ON(PageLRU(kpte_page));
	BUG_ON(PageCompound(kpte_page));
	if (pgprot_val(prot) != pgprot_val(ref_prot)) {
		if (level == 4) {
			set_pte(kpte, pfn_pte(pfn, prot));
		} else {
			/*
			 * split_large_page will take the reference for this
			 * change_page_attr on the split page.
			 */
			struct page *split;

			ref_prot2 = pte_pgprot(pte_clrhuge(*kpte));
			split = split_large_page(address, prot, ref_prot2);
			if (!split)
				return -ENOMEM;
			pgprot_val(ref_prot2) &= ~_PAGE_NX;
			set_pte(kpte, mk_pte(split, ref_prot2));
			kpte_page = split;
		}
		page_private(kpte_page)++;
	} else {
		if (level == 4) {
			set_pte(kpte, pfn_pte(pfn, ref_prot));
			BUG_ON(page_private(kpte_page) == 0);
			page_private(kpte_page)--;
		} else
			BUG();
	}

	/* on x86-64 the direct mapping set at boot is not using 4k pages */
	BUG_ON(PageReserved(kpte_page));

	save_page(kpte_page);
	if (page_private(kpte_page) == 0)
		revert_page(address, ref_prot);
	return 0;
}

/*
 * Change the page attributes of an page in the linear mapping.
 *
 * This should be used when a page is mapped with a different caching policy
 * than write-back somewhere - some CPUs do not like it when mappings with
 * different caching policies exist. This changes the page attributes of the
 * in kernel linear mapping too.
 *
 * The caller needs to ensure that there are no conflicting mappings elsewhere.
 * This function only deals with the kernel linear map.
 *
 * Caller must call global_flush_tlb() after this.
 */
int change_page_attr_addr(unsigned long address, int numpages, pgprot_t prot)
{
	int err = 0, kernel_map = 0, i;

	if (address >= __START_KERNEL_map &&
			address < __START_KERNEL_map + KERNEL_TEXT_SIZE) {

		address = (unsigned long)__va(__pa(address));
		kernel_map = 1;
	}

	down_write(&init_mm.mmap_sem);
	for (i = 0; i < numpages; i++, address += PAGE_SIZE) {
		unsigned long pfn = __pa(address) >> PAGE_SHIFT;

		if (!kernel_map || pte_present(pfn_pte(0, prot))) {
			err = __change_page_attr(address, pfn, prot,
						PAGE_KERNEL);
			if (err)
				break;
		}
		/* Handle kernel mapping too which aliases part of the
		 * lowmem */
		if (__pa(address) < KERNEL_TEXT_SIZE) {
			unsigned long addr2;
			pgprot_t prot2;

			addr2 = __START_KERNEL_map + __pa(address);
			/* Make sure the kernel mappings stay executable */
			prot2 = pte_pgprot(pte_mkexec(pfn_pte(0, prot)));
			err = __change_page_attr(addr2, pfn, prot2,
						 PAGE_KERNEL_EXEC);
		}
	}
	up_write(&init_mm.mmap_sem);

	return err;
}

/* Don't call this for MMIO areas that may not have a mem_map entry */
int change_page_attr(struct page *page, int numpages, pgprot_t prot)
{
	unsigned long addr = (unsigned long)page_address(page);

	return change_page_attr_addr(addr, numpages, prot);
}
EXPORT_SYMBOL(change_page_attr);

void global_flush_tlb(void)
{
	struct page *pg, *next;
	struct list_head l;

	/*
	 * Write-protect the semaphore, to exclude two contexts
	 * doing a list_replace_init() call in parallel and to
	 * exclude new additions to the deferred_pages list:
	 */
	down_write(&init_mm.mmap_sem);
	list_replace_init(&deferred_pages, &l);
	up_write(&init_mm.mmap_sem);

	flush_map(&l);

	list_for_each_entry_safe(pg, next, &l, lru) {
		list_del(&pg->lru);
		clear_bit(PG_arch_1, &pg->flags);
		if (page_private(pg) != 0)
			continue;
		ClearPagePrivate(pg);
		__free_page(pg);
	}
}
EXPORT_SYMBOL(global_flush_tlb);